1. Field of the Invention
The present invention relates to manually actuated, hydraulically operated tools of the type having working elements such as jaws or cutters which close over a workpiece and valving thereof. More particularly, the invention relates to a hand tool having a hydraulic circuit contained entirely within a housing containing two pistons. One piston converts manual input force to fluid pressure. The other piston converts fluid pressure to output force for imposing on the work. The tool enables three speeds of closure of jaw or corresponding tool movement at one input speed.
The field of endeavor most likely to benefit from this invention is the construction industry in that the device is specifically intended for use in creating effective hand tools which are often used in the building trades. However, the general fields of mechanical assembly and automotive repair could also benefit from the apparatus herein disclosed. For example, any process requiring crimping, bending, punching, cutting, pressing, etc. could significantly benefit from the performance characteristics of the instant hydraulic tool.
It can be appreciated that the potential field of use for this invention are myriad and the particular preferred embodiment described herein is in no way meant to limit the use of the invention to the particular field chosen for exposition of the details of the invention.
2. Description of Related Art
Gripping, clamping, pressing, and punching tools frequently employ hydraulic circuits for actuating solid moving parts of the tool. Hydraulics are quite practical to magnify manual force which can be applied to a work piece. Magnification of force is readily accomplished by varying respective areas of driving and driven components, such as a pump plunger and a driven piston, subjected to fluid pressure. Overpressure relief valves and manual release valves are also easily incorporated into hydraulic circuitry. However, the incorporation of such valving features has previously added considerable expense and complexity to the mechanism. This expense has been a major reason that small hydraulic hand tools have not achieved widespread success in the marketplace.
Thus, there is a need to provide hydraulic tool having valve structure of reduced complexity and cost.
An object of the present invention is to fulfill the needs referred to above. In accordance with the principles of the present invention, this objective is obtained by providing a bi-stable valve arrangement which includes a body having first and second opposing ends and constructed and arranged to define a passage between the body and another element so that the passage extends from the first end to the second end. A seal member is associated with the body. A first spring structure biases the seal member in a first direction and a second spring structure biases the seal member in a direction opposite the first direction. The first and second spring structures are constructed and arranged so that the seal member may seal the passage. The first and second spring structures have spring loads such that under certain fluid pressure conditions on the first and second ends of the body, the seal member moves against the bias thereon to permit fluid flow through the passage in one direction, and under different pressure conditions on the first and second ends of the body, the seal member moves against the bias thereon to permit fluid to flow through the passage in a direction opposite the one direction.
In accordance with another aspect of the invention a check valve includes a body having a passage therein in open communication with a source of fluid. A spring support structure is coupled to and extends from the body. A seal structure includes an elastomer seal member disposed generally adjacent to the passage. A spring is supported by the spring support structure and biases the seal structure so that the seal member is in a sealing position preventing fluid from the source from exiting the passage. A load of the spring is such that when fluid pressure in the passage exceeds the spring load, the seal structure moves against the bias of the spring, permitting the seal member to move to an unsealing position to permit fluid to exit the passage.
In accordance with yet another aspect of the invention, a pressure releasing valve arrangement includes a valve structure having a valve member constructed and arranged to be disposed in a housing chamber of an element to seal an opening in the element. The opening communicates a fluid pressure chamber of the element with the housing chamber. The valve member separates the fluid pressure chamber from the housing chamber. The valve structure is constructed and arranged to be operatively associated with a movable member mounted for movement within the element. A spring biases the valve member towards a sealing position to seal the opening. When fluid pressure in the fluid pressure chamber reaches a pre-determined pressure, the valve member moves from the sealing position against the bias of the spring to unseal the opening permitting fluid pressure in the fluid pressure chamber to be reduced below the pre-determined pressure, due to fluid entering the housing chamber. Further, when the movable member moves to an over-travel condition, the valve structure is engaged by the movable member and moved therewith which causes the valve member to move from the sealing position to unseal the opening.
Other objects, features and characteristic of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
Various other objects, features, and advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, wherein like parts are given like numerals.